01 - Heat a non-stick skillet over medium heat. Add sliced shiitake mushrooms and sauté for 5-6 minutes, stirring occasionally, until tender. Set aside to cool.
02 - Prepare all fresh vegetables (avocado, carrot, cucumber, bell pepper, spinach, scallions, herbs) and arrange them within easy reach.
03 - Fill a shallow dish with warm water. Dip one rice paper sheet in the water for 10-15 seconds until just softened, then carefully lay flat on a clean kitchen towel or board.
04 - Lay a small handful of spinach or lettuce in the center of the rice paper. Top with a few slices each of avocado, sautéed shiitake, carrot, cucumber, bell pepper, scallions, and a sprinkle of herbs.
05 - Fold the bottom of the rice paper over the filling, then fold in both sides and roll up tightly to close. Repeat with remaining ingredients (should make 8 rolls).
06 - For the dipping sauce, whisk all ingredients together in a small bowl until smooth. Adjust consistency with water if needed.
07 - Serve spring rolls immediately, whole or sliced in half, with dipping sauce on the side.